Gravity Probe B

Testing Einstein's Universe

WEEKLY HIGHLIGHTS FOR WEEK ENDING 5 SEPTEMBER
2003:

VANDENBERG AIR FORCE BASE OPERATIONS
The following activities were completed at VAFB this past week:

Conditioning of the dewar to a superfluid state has begun. Conditioning
is the process of taking liquid helium at a temperature of about 4 Kelvin
to a colder state, known as superfluid, which will allow the helium to last
throughout the duration of the mission. Getting the dewar 95% full of superfluid
helium is a long, iterative process of repeated evacuations and fills.

Currently, the dewar has successfully been taken to sub-atmospheric pressure,
and the temperature has dropped below the normal boiling point of helium.
The dewar is currently 76.5% full of helium, at a temperature of 2.11 Kelvin.
Over the next two weeks, the dewar will be filled to 95% capacity, with a
corresponding temperature drop to 1.65 Kelvin.

Photo: The GP-B Cryo group performing a sub-atmospheric transfer of liquid
helium into the dewar's main tank.